It says the 12 men left Nauru on the weekend on a charter flight that also included another 21 Sri Lankans who had been detained in Western Australia.

Earlier last week, another four Sri Lankans went home rather than remain in the Nauru detention camp.

The temporary facility on Nauru has been strongly criticised by the regional representative of the UNHCR, Richard Towle, who said the inmates faced a toxic combination, with the legal uncertainty, the delays in their refugee processing and the harsh environment.

The Australian Government has dismissed the criticism and says the inmates receive appropriate care.